Preferably, conventional office chairs are designed to provide significant levels of comfort and adjustability. Such chairs typically include a base which supports a tilt control mechanism to which a seat assembly and back assembly are movably interconnected. The tilt control mechanism includes a back upright which extends rearwardly and upwardly and supports the back assembly rearwardly adjacent to the seat assembly. The tilt control mechanism serves to interconnect the seat and back assembly so that they may tilt rearwardly together in response to movements by the chair occupant, and possibly to permit limited forward tilting of the seat and back. Further, such chairs typically permit the back to also move relative to the seat during such rearward tilting.
The chair also is designed to provide additional support assemblies to provide further support to the occupant's body at various locations thereof. In this regard, support assemblies have been provided which attempt to provide adjustable support to the lower back of the user in the lumbar region thereof. However, one difficulty associated with the design of conventional office chairs is the fact that office workers have different physical characteristics and comfort preferences such that it is difficult to design a single chair configuration that satisfies the preferences of the different individuals who might purchase such a chair.
To improve comfort, it is known to provide lumbar supports which allow for adjustment of the elevation of the lumbar support along the back of the user. However, often times, such lumbar supports may be found uncomfortable to various individuals since they tend to provide localized pressure on the lumbar region of the back.
Accordingly, it is an object of the invention to overcome disadvantages associated with prior lumbar support arrangements and to develop a lumbar support using test data that represents the actual, quantifiable comfort preferences of a group of test occupants.
The invention relates to a chair having an improved back assembly which provides support to the back region of the chair occupant. The back assembly of the invention includes a lumbar support arrangement preferably disposed in the lumbar region of the back which is adjustable vertically to accommodate different sizes of chair users.
The back assembly is of the type having an open annular frame with a suspension fabric extending therebetween to close the central opening of the back frame. Since this suspension fabric is only a thin layer of material, the support provided by the lumbar support assembly is more readily felt and it is more critical to provide a comfortable lumbar support pad.
In an effort to provide optimum support to the back of the chair occupant, the lumbar support pad itself is formed of concentric support rings wherein radially adjacent pairs of such rings are flexibly joined together by connector webs extending therebetween. To a certain extent, each ring can independently move or is at least supported independently relative to an adjacent ring. This allows for greater variations in support pressure being applied by each ring to the back of the occupant, and the lumbar support pad more readily adjusts to the shape of the occupant's back. The support pad therefore provides an adjustable and optimized amount of asymmetric support pressure while maintaining a proper ergonomic posture to the seated occupant. Further, the selected locations of the connector webs provides support to areas of the pad that have been determined to be most preferable as a result of the test apparatus and method of the invention.
Additionally, the lumbar support pad is carried by a support arm formed similar to a leaf spring wherein the support arm has a vertically elongate opening in the middle thereof to separate the left and right halves of the support arm from each other along a substantial portion of the length of each support arm. While the support arm may bend rearwardly in response to the occupant or at least resiliently resist such movement, the bending point for each of the left and right halves is independently adjustable so that the support provided to the lumbar support pad is asymmetric with respect to the left and right halves of the support pad. This support arm provides asymmetric support to the lumbar support pad and each half thereof provides support pressures which are more independent of the other. The chair occupant therefore can more accurately adjust the support provided by the support pad asymmetrically wherein it has been found through testing that this asymmetric support provides improved comfort to the chair occupant.
The invention further relates to the test apparatus and process for determining the optimum design of the lumbar pad. The test apparatus includes a test rig on a chair which determines the contour and pressure map of the lumbar support preferred by the occupant when seated.
The test rig has a support plate rearwardly of and facing toward the lumbar area of the occupant's back. The support plate includes an array of adjustable testers which project toward and contact the occupant's lumbar area. The preferred testers are arranged in a rectangular grid pattern of rows and columns and include a plunger like contact pad. The pad is spring-loaded and supported on a plunger rod. The plunger rod is attached on the support plate and movable relative thereto to adjust the resiliently biased pressure being applied by the contact pad to the lumbar area. An FSA pressure mapping system is further used to verify and quantify the pressure being applied to the lumbar.
As a result of this pressure mapping testing process, the above-described lumbar pad was developed to provide optimum support to the occupant. It will be understood that the test process was primarily directed to development of the lumbar pad although other support pads or structures in the back and/or seat could be developed through the test apparatus and process of the invention.
Other objects and purposes of the invention, and variations thereof, will be apparent upon reading the following specification and inspecting the accompanying drawings.
Certain terminology will be used in the following description for convenience and reference only, and will not be limiting. For example, the words “upwardly”, “downwardly”, “rightwardly” and “leftwardly” will refer to directions in the drawings to which reference is made. The words “inwardly” and “outwardly” will refer to directions toward and away from, respectively, the geometric center of the arrangement and designated parts thereof. Said terminology will include the words specifically mentioned, derivatives thereof, and words of similar import.